1. Field of the Invention
This invention relates to a bidirectional road traffic sensor which is capable of simultaneously monitoring two or more lanes of traffic for counting and/or classifying individual vehicles.
2. Description of the Prior Art
The term "road traffic" is used to include wheeled vehicles such as automobiles, having flexible or pneumatic tires covering a substantial area of the roadway in supporting the weight of the vehicle on wheels spaced-apart transverse to the direction of movement of the vehicle, and includes automotive vehicles in a toll collection lane or in a low speed vehicle weighing lane for example.
One of the problems facing highway engineers is the necessity to provide adequate traffic control systems which can readily handle the ever increasing loads of automotive traffic. Vital to the solution of this problem is the need for continuous accurate information concerning the number of vehicles and/or type (classification) of vehicles passing over a particular stretch of highway. Often, in order to provide maximum utilization of given highway facilities, it is necessary to use a particular single traffic lane for vehicles moving in both directions, e.g., the center lane of a three-lane highway, or multi-lane highways using all but one lane for traffic in a particular direction during rush hours.
It is frequently necessary in the control of vehicular traffic to provide means for the selective detection and/or counting of vehicles in accordance with their direction of travel as they pass through a defined detection area.
The U.S. Federal Highway Administration and other government agencies both in Canada and in the U.S.A., often require the submission of reports concerning truck travel at specific locations on roadways before authorizing funding for the repair and improvement of such roadways. Such reports are typically submitted in a format known as the Federal Highway Administration vehicle Classification Scheme. A number of classifying machines are currently in manufacture. Typically, they require two axle detector inputs positioned a known distance apart. The machine measures the time between axle actuations, calculates the speeds at which the axles are travelling, counts the number of axles travelling at the same rate of speed, and then, depending upon results, records the vehicle type in a predetermined classification bin. Such studies are typically undertaken over a continuous 24 hour period and are broken down into one hour increments. Portable axle detector devices manufactured and available today vary greatly in cost, durability, limitations of operation and set up procedure difficulty.
Heretofore, in traffic counting systems on a multi-lane highway, a treadle switch was embedded in each lane of the highway for actuation by the wheels of a vehicle, and each treadle controlled a circuit operating a counter to count the vehicle axles passing over the lane. In such systems it was necessary to add the counts of each counter in order to obtain the total count in all lanes. Furthermore, the initial cost of such systems proved expensive, and the operating expenses attached thereto, also proved to be slightly higher than most road authorities had anticipated.
Such treadle switch traffic counting system are now obsolete. In more recent traffic counting systems, it has been found that vehicles usually cross the sensing mechanisms in different lanes, simultaneously or substantially so, so that the time between actuation of the sensors is less than it takes to operate a counter.
The art replete with patents directed to traffic counting in a single lane of traffic and/or for unidirectional traffic. Typical examples include the following: D. Katz U.S. Pat. No. 1,992,214 patented on Feb. 26, 1933; Power U.S. Pat. No. 2,067,336 patented Jan. 12, 1937; C. D. Cutler U.S. Pat. No. 2,161,896 patented Jun. 13, 1939; J. M. Paver U.S. Pat. No. 2,163,960 patented Jun. 27, 1939; R. R. Armstrong U.S. Pat. No. 2,244,933 patented Jun. 10, 1941; G. V. Nolde U.S. Pat. No. 2,319,153 patented May 11, 1943; E. J. Schulenburg U.S. Pat. No. 2,823,279 patented Feb. 11, 1958; H. A. Wilcox U.S. Pat. No. 2,885,508 patented May 5, 1959; U.S. Pat. No. 2,909,628 to Cooper; J. P. Roscoe U.S. Pat. No. 2,922,003 patented Jan. 19, 1960; H. A. Wilcox U.S. Pat. No. 3,188,422 patented Jun. 8, 1965; U.S. Pat. No. 3,486,008; G. Fischel U.S. Pat. No. 3,732,384 patented May 8, 1973; V. Necloff U.S. Pat. No. 3,927,389 patented Dec. 16, 1977; C. Abhodanto U.S. Pat. No. 4,013,851 patented Mar. 22, 1977; C. M. Tromp U.S. Pat. No. 4,799,381 patented Jan. 24, 1989; A. Buckley U.S. Pat. No. 4,839,480 patented Jun. 13, 1989; B. Sobut U.S. Pat. No. 4,862,163 patented Aug. 29, 1989; J. R. Fisher U.S. Pat. No. 5,115,109 patented May 19, 1992; J. L. Banke Canadian Patent No. 727,292 patented Feb. 1, 1966; H. C. Kendall et al. Canadian Patent No. 749,552 patented Dec. 27, 1960; S. Iwamoto et al Canadian Patent No. 902,208 patented Jun. 6, 1972; and W. T. Lawrence Canadian Patent No. 1,048,121 patented Feb. 6, 1979.
The patent literature also purported to provide solution to the problem of means for counting and totalizing, on a single counter, the vehicular traffic on a multi-lane highway. Among the patents allegedly providing solution to such problem are the following:
B. Cooper U.S. Pat. No. 2,268,925 patented Jun. 6, 1942, provided a device which included, in combination, a plurality of switches, and an electromagnetic counter having an electromagnet. Means were provided to energize the electromagnet once for each actuation of any of the switches when the period between actuations of different switches was either greater or less than the time it took for the counter to operate in making a count. The system also included means to prevent more than one energization of the electromagnet upon actuation of a switch, irrespective of the duration of actuation of that switch.
N. A. Bolton U.S. Pat. No. 3,079,077 patented Feb. 26, 1963 provided separate detection and counting of a plurality of objects simultaneously passing a fixed monitoring point. The patented system included a plurality of vehicle detection means located across a passageway. Such means defined respective detection zones more closely spaced successively than the width of any vehicle. Each zone was constructed and arranged as to provide a momentary output signal upon the passage of a vehicle through the respective detection zone. Counting means were provided for counting discrete input signals successively applied to its input circuit. Means were provided for coupling each vehicle detection means to the input circuit, such coupling means responded to substantially simultaneous output signals from vehicle detectors respectively defining adjacent detection zones by supplying a single input signal to the input circuit of the counting means. On the other hand, such coupling means responded to substantially simultaneous output signals from vehicle detectors respectively defining non-adjacent detection zones by supplying time-spaced input signals to the input circuit. In this way, a single vehicle passing simultaneously through adjacent detection zones was counted singly by the counting circuit means but a plurality of vehicles passing simultaneously through non-adjacent detection zones were separately counted by the counting circuit means.
N. A. Bolton U.S. Pat. No. 3,109,157 patented Oct. 29, 1963 provided a system for the selective detection, counting and control of automotive traffic travelling past a particular point in more than one direction. The patented system included at least two successive detection zones. A plurality of vehicle responsive means was provided, each means defining a respective one of the detection zones and each being operated to a distinctive condition by the passage of a vehicle through the respective detection zone. Direction detection means were also provided, along with means governed by the vehicle-responsive means for the respective zones for operating the direction detection means to a distinctive condition indicative of the passage of a vehicle in one particular direction along the roadway only for a particular corresponding sequence of vehicle detections by the two vehicle responsive means. Vehicle registering means were provided, along with control means for the vehicle registering means governed jointly by the vehicle-responsive means for the respective detection zones, and by the direction detection means for registering the passage of the vehicle moving in a particular direction only when the direction responsive means had been controlled to the distinctive condition and the second-operated of the vehicle detection means for the particular direction of vehicle travel had been restored to its normal condition. Registration prevention means were provided for preventing, when operated from its normal condition, the registration of a count by the vehicle-registration means. Means were provided for operating the registration-prevention means only when the interval between the successive operations of the two vehicle-detection means in response to a single vehicle was substantially in excess of that normally expected for a vehicle passing through the detection. Such operating means served to restore the registration-prevention means when the vehicle was detected by the second-operated vehicle detection means.
N. A. Bolton U.S. Pat. No. 3,141,612 patented Jul. 21, 1964 provided a system for the selective detection of vehicles passing over either or both of a multiple number of lanes and through a predetermined detection area according to their direction of travel. The patented system included at least two spaced first and second vehicle-detection zones, each zone being defined by a respective vehicle-detector means. Each vehicle detector means was distinctively controlled by the passage of a vehicle through the respective detection zone. Vehicle-registering means were provided which were governed by both the vehicle-detector means for registering the passage of a vehicle in a particular direction as the vehicle while moving in the particular direction sequentially traverses the successive detection zones. The registering means normally registered the passage of the vehicle when the vehicle detector means for the second of the detection zones to be traversed sensed that the vehicle had vacated the second detection zone. Means were provided which were distinctively controlled by the vehicle-detector for the first detection zone when the first detection zone became occupied at a time when the second detection zone was still occupied. Such last-named means, when in the distinctive condition, prevented registration of a first vehicle upon its vacating the second detection zone at a time when the first detection zone was occupied by a second vehicle and permitted registration of the first vehicle only provided that thereafter both the detection zones became simultaneously occupied. Such means was restored to its normal condition by the vehicle-registering means when the first vehicle had been registered. In this way, a vehicle reversing its direction even after having vacated the first detection zone was not registered.
G. P. Gibson U.S. Pat. No. 4,901,334 patented Feb. 13, 1990 provided counters or tallying devices which were actuated by vehicle passage over a sensing means in place on a roadway surface, for selective lane use. The patented traffic counter apparatus included a housing assembly including a base adapted for securement to the roadway surface between two traffic lanes. A housing was provided having a low profile to the roadway and having inclined exterior walls. Means were provided for removably mounting the housing to the base, the housing defining a chamber closed by the base and constructed of material to withstand being run over by any roadway vehicle. A road tube was provided for disposition in a traffic lane. The road tube had an end attached to the housing assembly. Pressure responsive transducer switch means were provided in the chamber which were responsive to air pressure changes in the road tube caused by vehicle passage thereover, in order to produce electrical pulses. Signal transmitting means were provided in the chamber connected to, and actuated by, the pressure responsive switch means for transmitting the electrical pulses. Tally means were provided remote from the housing assembly, which was triggered by the pulses from the signal transmitting means.
J. W. Reed U.S. Pat. No. 5,239,148 patented Aug. 24, 1993 provided a portable apparatus for discriminating the counting of vehicular traffic in multiple lanes. The patented apparatus was in the form of a traffic counting cord. Such cord had a plurality of sections designed to be identical in physical characteristics, set-up procedures, durability and performance as a road tube. Each section had a portion with conductive upper and lower members and a portion with non-conductive upper and lower members. The upper and lower members were separated by resilient, non-conductive material. Embedded within the members were a plurality of wires insulated with nylon or other material and at least one non-insulated wire which was in contact with the conductive member. A count occurred when traffic impacting the cord caused the upper and lower members of a section to make contact. Individual counts for each lane could be obtained by cross-wiring the sections, so that the uninsulated conductors of each section were routed to a counter through insulated conductors or wires of the other sections. Any even or odd number of lanes, typically four, six, or eight lanes could therefore be accommodated, although there was no theoretical limit.